A 100 G Digital Signal Processor (DSP) is used for processing data and signals in a 100 G optical module of a 100 G line card, and is a critical component of the 100 G optical module. A frequency offset estimation part is a critical part of the 100 G DSP, and mainly performs frequency offset estimation so as to compensate frequency offsets of signals. Since the 100 G DSP has a processing speed much higher than that of the currently used 40 G DSP, the existing frequency offset estimation techniques, when applied in the 100 G DSP, may have a substantially low processing efficiency.